Back in the old days, I used to set ignition timing by advancing it to achieve maximum revs at tickover (with the vacuum plugged) and then backing it off to just avoid pinking.
My old Kia Pride has got a carburettor (with lots of electricary gubbins) and a distributor, but no points.
The handbook gives an ignition timing of two degrees BTDC (+ or - one), but with no other criteria.
I've also seen an advised setting of '9-11 @ 700' but again with no criteria.
The timing was set at about 6 degrees BTDC around 700 RPM with the vacuum plugged when I got it, which I've changed to about 4 degrees BTDC as a compromise. It's made no appreciable difference changing it. I've got an old Xenon timing lamp to measure it.
I don't know if it's fitted with a knock sensor.
I use it for trialling (maximum torque at minimum revs) and grass autotesting (7K RPM) as well as general road use.
Any suggestions as to setting the optimum ignition timing for different uses would be appreciated.
It's quite easy to mark up different positions on the distributor and quickly adjust it.
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On your own [cracked] head be it.
To optimize the timing at any particular revs. [Around 2,000 is about right for road use.]
Connect an analogue hand-held rev counter; loosen distributor; start engine.
Adjust throttle stop to around 2,000 revs. Slowly advance the dizzy and you'll see the revs first increase, then level out, then drop as a misfire begins.
Gradually retard from there until you achieve the peak reading that you got on the way up. Retard it down another 50 revs, which usually requires quite a turn, then lock-up the dizzy there.
[And that hideous half-carb/half singlepoint injection unit with an electronic main jet was, thankfully, unique to that engine.]
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Thanks Screwloose.
You're not a fan of my carb then? ;>) I've taken a look at it and backed off. I sincerely hope I never get any problems with it. It could explain the exhaust emissions. My local MOT station are used to it now, after initial disbelief. It passes with a Lambda reading of 1.2, it's pass range is 0.95 - 1.3.
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Many older cars were more susceptible to 'pinking' than others - the ford pinto springs to mind.
Some manufactures state ignition timing should be set at say 3000rpm with vac disconnected and that method is far more accurate than say setting it at 6btdc @ 800rpm.
But to do that, you would need a timing light with an in-built advance meter, and to know what the ignition advance should be at that engine speed.
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KIA Pride - 94 1324 Optimum ignition timing - Screwloose
